53. The most common intoxications in small animal practice (kumarins, ethylene glycol, drugs, biotoxins)

What are examples of coumarins?

Warfarin & Superwarfarin, Brodifacoum

What is the effect of coumarins on the body?

Anticoagulant action upon ingestion

What are the sources of coumarin poisoning?

Ingestion of rodenticides (baits) or of poisoned dead rats

What is the pathogenesis of coumarin poisoning?

Cause reduction in vitamin K-dependent clotting factors (II, VII, IX, X)

They prevent prothrombin production in the liver, prolong clotting time, and damage capillaries, causing massive internal bleeding

What is the difference in toxicity between warfarin and superwarfarin?

Warfarin must be ingested repeatedly to induce poisoning, while superwarfarin is highly toxic after a single dose

What are the clinical signs of coumarin poisoning?

Lethargy, dyspnoea, pale gums, coughing, bleeding (epistaxis, melaena, internal haemorrhages into skin, organs, and joints)

How is coumarin poisoning diagnosed?

Reduced prothrombin time, prolonged clotting (Normal = Dog: 90-120 sec; Cat: 60-80 sec) & bleeding times.

However, treatment is usually started immediately based on suspicion of rodenticide ingestion

How is coumarin poisoning treated?

1. Administration of transfusions (clotting factors). Plasma w/ clotting factor, blood transfusion.

2. Synthetic vitamin K or K1

   1. Warfarin: 1 mg/kg vitamin K1

   2. Brodifacoum: 10 mg/kg vitamin K1

3. Emesis: apomorphine (dog), xylazine (cat)

What is ethylene glycol?

Antifreeze used in cars and radiators

Why is ethylene glycol dangerous?

It tastes sweet and may be the only available liquid in cold weather

How much ethylene glycol is lethal to cats and medium-sized dogs?

1 tablespoon is lethal to cats, and 5 tablespoons is lethal to a medium-sized dog

What organs are affected by ethylene glycol poisoning?

GIT, nervous system, and kidneys

What is the toxic metabolite of ethylene glycol and what does it do?

Oxalic acid, which binds to calcium, forming calcium oxalate crystals

What are the key pathological changes caused by ethylene glycol?

Severe metabolic acidosis (due to oxalic acid) and tubular damage (due to toxins and calcium oxalate crystals)

What are the three stages of ethylene glycol poisoning?

1. Stage 1 (within 30 minutes)

2. Stage 2 (12-24 hours after ingestion)

3. Stage 3 (36-72 hours after ingestion)

What are the clinical signs of Stage 1 ethylene glycol poisoning?

Lethargy, vomiting, incoordination, excessive urination, excessive thirst, hypothermia, seizures, and coma

What are the clinical signs of Stage 2 ethylene glycol poisoning?

Apparent improvement, but the animal becomes dehydrated, developing tachycardia and tachypnoea

What are the clinical signs of Stage 3 ethylene glycol poisoning?

Severe kidney dysfunction (swollen, painful kidneys, anuria), pulmonary oedema, progressive depression, lethargy, vomiting, seizures, coma, and death

How is ethylene glycol poisoning diagnosed?

1. Urine analysis (crystalluria with blood, pus and casts)

2. Ultrasound (renal hyperechogenicity due to calcium oxalate crystals)

3. Measuring blood ethylene glycol, creatinine and BUN concentration

How is ethylene glycol poisoning treated?

5% IV or 40% PO ethanol solution or fomepizole (an alcohol dehydrogenase inhibitor) and aggressive fluid therapy

What are examples of drugs causing intoxications?

1. ACE inhibitors (anti-hypertensive drugs)

2. Anti-depressive drugs

3. Marihuana

4. Paracetamol

What can an overdose of anti-hypertensive drugs (ACE inhibitors) cause?

Hypotension

What can an overdose of anti-depressants cause?

Serious neurological problems or severe tachycardia, hypertension, and hyperthermia

What are the clinical signs of marijuana (THC) toxicity?

Tremors, vocalisation, ataxia, and vomiting

How is marijuana toxicity treated?

Supportive care, including fluids (WATER)

Why is paracetamol dangerous for cats?

They lack the necessary liver enzymes to metabolise it efficiently

What are the toxic effects of paracetamol in cats?

Hepatotoxicity, Heinz body formation, haemolysis, and methaemoglobinaemia

What are the clinical signs of paracetamol toxicity in cats?

Dyspnoea, pale mucous membranes, pigmenturia, oedema of the face and paws, and jaundice

How is paracetamol toxicity in cats treated?

Gastric lavage, activated charcoal, and the antidote N-acetylcysteine

What are biotoxins?

Poisons of plant or animal origin, including food intoxications

Give examples of biotoxins.

1. Snake venom

2. Wasp stings

3. Poisonous plants

4. Toxins from certain foods

5. Blue-green algae

What is the effect of snake venom?

Viperidae venom → haemolysis

What are some effects of consuming poisonous plants?

Vomiting and gastrointestinal upset

Which flowers are particularly dangerous to cats?

Bell flowers (especially foxglove, which can cause heart failure) and lilies (causing renal failure)

What are examples of foods which may cause intoxications?

1. Chocolate

2. Grapes and raisins

3. Onion and garlic

4. Black tea and coffee

What is the toxic component of chocolate and what are its effects?

Theobromine, which is slowly processed by dogs, leading to build-up and causing muscle tremors, seizures, irregular heartbeat, internal bleeding, or heart attack

What are the clinical signs of chocolate toxicity?

Hyperactivity, vomiting, diarrhoea, shivering, tachycardia, and hypovolaemia

How is chocolate toxicity treated?

Infusion therapy and activated charcoal

What are the toxic effects of grapes and raisins?

Acute kidney failure

What are the clinical signs of grape and raisin toxicity?

Vomiting, diarrhoea, and lethargy

What are the toxic effects of onions and garlic (Allium family)?

Damage to erythrocytes (Heinz body formation) leading to haemolysis

What are the clinical signs of intoxications with onion and garlic?

Vomiting, brown urine, lethargy

What are the toxic effects of black tea and coffee?

Caffeine (a purine alkaloid) is biotransformed into cytotoxic pyrroles, especially affecting liver cell nuclei, leading to liver failure

What are the toxic effects of blue-green algae (cyanobacteria)?

Damage to the GIT, liver, kidneys, and nervous system

What are the clinical signs of blue-green algae toxicity?

Vomiting, abdominal pain, neurological signs (minutes/hours after exposure), salivation, dyspnoea, seizures, and coma

What other coumarins exist other than warfarin and super warfarin?

Brodifacoum

How long after treatment of ethylene glycol poisoning should euthanasia take place if there is no improvement?

24 hours

What is the dose of vitamin K1?

• Warfarin: 1 mg/kg

• Brodifacoum: 10 mg/kg